$ E = \left[\begin{array}{rrr}1 & 2 & 2 \\ 0 & 2 & 0 \\ 2 & 0 & 0\end{array}\right]$ What is $ E^{-1}$ ?
$ = \left[\begin{array}{rrr}0 & 0 & \frac{1}{2} \\ 0 & \frac{1}{2} & 0 \\ \frac{1}{2} & -\frac{1}{2} & -\frac{1}{4}\end{array}\right]$